Although processes analogous to the chlorination of ilmenite or rutile to make titanium tetrachloride with subsequent oxidation to make titanium dioxide and recycle chlorine using bauxite, clay or other aluminous materials have been proposed frequently, there is no present commercial operation embodying this cycle. Though it is necessary to have a fine, uniform and well-controlled pigment particle size for titania pigment, the need for aluminas of similar particle size, or particle sizes resulting from oxidation is not evident. Either aluminas of high surface area currently in use, or aluminas of negligible surface area, but of easily handled particle size, would be desired from the oxidation cycle proposed.
In order to produce aluminas similar to those currently in use in some aluminum pot-lines, it is necessary to hydrolyse the aluminum chloride produce from the chlorination of aluminous ores. Although this has the disadvantage of making HCl which is not directly usable for recycle of chlorine values, it is possible to convert hydrogen chloride into chlorine, though at an economic penalty. The amount of oxygen necessary to convert aluminum chloride to chlorine is the same whether a direct oxidation route is taken or the HCl route is taken. Although there are several ways to convert HCl to chlorine, including the non-oxidative Uhde electrolysis and the more recently developed Kel-Clor process as well as the traditional Deacon process, none of these are particularly compatible with the high temperature chlorination techniques which produce aluminum chloride.
Other approaches to alumina production through the hydrated chloride route have and are currently being investigated. These lead to the hydrolysis of hydrated aluminum chloride, need additional excessive amounts of heat and require the extensive equipment investment accompanying any leaching process used to open minerals. It is to avoid slow and high volume processes that the high temperature chlorination techniques were developed. Chloride processes have found success and such concepts have been used in the titanium pigment industry since about 1950. The future of the aluminum industry is thought by many to be dependent not only upon the replacement of high grade bauxites with lower grades (highly siliceous) or with clay and other aluminum sources but upon reduction of the electrical power requirement by substituting aluminum chloride for aluminum oxide in the reduction stage with the elimination of fluorides as well.